450lbs bike + 210lbs driver = 660 lbs
660lbs/39psi ~= 17 squareinch.
Of course its not a fair equation for front/rear distribution*, and that for me is the rear pressure, but if you try to keep this virtual contact patch at 17si for grip and shape, heating and wear, the weight you intend to put should dictate the pressure. Simple.

*The front pressure is a few psi below rear since we dont quite know the proportion, but you could find that easily rolling each wheel on a body scale while sitting on the bike (might want to try using front and read stands if they are secure enough).

You're on a relatively light sportbike , so you should be around 32 front and rear , assuming average ability. If you just cruise , about 36.